1 – Correct
Those who had been taking cannabis for 15 years recalled less words than those who had been taking it for 7 years. Also, those who had been taking cannabis for 7 years recalled less words than those who had never smoked cannabis. This shows that long-term smoking had an impact on the ability of a person to learn and remember.
2 – Correct
Another explanation could be that cannabis’ effect lasts for more than 24 hours which explains the results that we got.
3 – Correct
This could also be true. Difference in IQs could be the reason why such results were obtained, independent of cannabis smoking.
Since all three statements are correct, E is the answer.